Somatomedin-C is a growth hormone dependent basic peptide which we have isolated in small quantities from large quantitites of outdated human plasma. A primary objective of this project is to complete the amino acid sequence of this peptide and determine which portions of the molecule are required for its growth-promoting activity and insulin-like properties, respectively. Biological activity will be correlated with the chemical structure of reduced and alkylated derivatives, of fragments derived by chemical and enzymatic cleavage, and of chemically synthesized fragments. The goal of this endeavor will be to synthesize sufficient quantities of the native peptide or an active fragment thereof to permit biological studies on a much broader scale than is now possible. Simultaneous efforts will be made to improve present preparative methods from plasma to obtain much larger yields for our ongoing biological studies and to meet the pressing demands of other investigators. Attempts to make somatomedin-C more antigenic will be made by complexing it with albumin and other substances. Biological studies will be addressed to determining the physiological role of somatomedin-C, its mechanisms of formation and degradation, the cell types which are responsive to its anabolic and mitogenic effects, and the intracellular events which it triggers. These studies will be initially carried out in cell cultures of human skin fibroblasts and later extended to cultures of chondrocytes and other cell types. In vivo pharmacologic effects of somatomedin-C will be studied in hypophysectomized animals to determine the likelihood of therapeutic usages.